[Effects of ditch-buried organic matter and irrigation amount after anthesis on the photosynthetic characteristics and yield of maize.] / æœ‰æœºç‰©æ²ŸåŸ‹è¿˜ç”°æ¨¡å¼ä¸ŽèŠ±åŽçŒæ°´é‡å¯¹çŽ‰ç±³å ‰åˆç‰¹æ€§å’Œäº§é‡çš„å½±å“.

Managements of organic matter and irrigation after anthesis will increase the capacities of water conservation and supply in maize field, with consequences on photosynthetic performance and yield under water-saving condition. We analyzed the gas exchange parameters and the performance of the photosystem 2 of ear leaves, and yield of maize cultivars Zhengdan 958, under three modes of ditch-buried organic matter (no straw returned: M0, wheat straw returned: M1, mixtures of cow manure and wheat straw returned: M2) before seeding with two irrigation levels after anthesis (normal irrigation: W1, water-saving irrigation: W2). The results showed that M2 treatment significantly increased photosynthetic capacity and dry matter accumulation after anthesis compared with M1 treatment. Compared with water-saving irrigation, normal irrigation enhanced the photosynthesis of ear leaves. M2W1 treatment significantly increased net photosynthetic rate (Pn), stomatal conduc-tance (gs), transpiration rate (Tr), and performance of photosystem 2 (Φpo and ωo) of ear leaves after anthesis, while reduced intercellular CO2 concentration (Ci). In addition, M2W1 treatment significantly increased light utilization efficiency and maintained higher photosynthetic properties in ear leaves, and significantly increased dry matter accumulation and grain yield. Water-saving irrigation reduced photosynthetic performance of ear leaves, which declined the yield. But compared M2 with M0, water use efficiency, grain growth rate and yield increment under water-saving irrigation were higher than those under normal irrigation. Thus, mixtures of cow manure and wheat straw returned combined with normal irrigation could significantly increase photosynthetic properties of ear leaves and dry matter accumulation, which were the major reasons for yield enhancement. Importantly, the mixture of cow manure and wheat straw returned combined with water-saving irrigation could decrease the loss of crop yield resulted from lower irrigation.

[Effects of different straw recycling and tillage methods on soil respiration and microbial activity].

To explore the effects of different tillage methods and straw recycling on soil respiration and microbial activity in summer maize field during the winter wheat and summer maize double cropping system, substrate induced respiration method and CO2 release method were used to determine soil microbial biomass carbon, microbial activity, soil respiration, and microbial respiratory quotient. The experiment included 3 tillage methods during the winter wheat growing season, i.e., no-tillage, subsoiling and conventional tillage. Each tillage method was companied with 2 straw management patterns, i.e., straw recycling and no straw. The results indicated that the conservation tillage methods and straw recycling mainly affected 0-10 cm soil layer. Straw recycling could significantly improve the microbial biomass carbon and microbial activity, while decrease microbial respiratory quotient. Straw recycling could improve the soil respiration at both seedling stage and anthesis, however, it could reduce the soil respiration at filling stage, wax ripeness, and harvest stage. Under the same straw application, compared with conventional tillage, the soil respiration and microbial respiratory quotient in both subsoiling and no-tillage were reduced, while the microbial biomass carbon and microbial activity were increased. During the summer maize growing season, soil microbial biomass carbon and microbial activity were increased in straw returning with conservation tillage, while the respiratory quotient was reduced. In 0-10 cm soil layer, compared with conventional tillage, straw recycling with subsoiling and no-tillage significantly increased soil microbial biomass carbon by 95.8% and 74.3%, and increased soil microbial activity by 97.1% and 74.2%, respectively.

[Effects of different maize straw-returning modes on the soil respiration in a winter wheat field].

By using static chamber-TGC method, an in situ observation was conducted in a 10-year conservation tillage winter wheat field to study the effects of different maize straw-returning modes on the soil respiration. The soil respiration had a significant positive correlation with the stubble height of maize straw, and two peaks were observed in wheat growth period. Under no tillage and no straw-returning, the soil respiration was 72.5% of that under no tillage with all straw-returning, and the soil respiration under conventional tillage and no straw- returning was 76.5% of that under conventional tillage with all straw-returning. The soil respiration was significantly positively correlated with the soil temperature and soil organic carbon at 20 cm depth, but no significant correlation with the soil organic carbon at 40 cm depth. A correlation was also observed between the soil respiration and soil moisture. The diurnal soil respiration in the treatments of all straw-returning presented a single-peak curve, with the peak at 18:00. There was a similar variation trend of soil temperature and soil respiration at the depth of 20 cm. Among the treatments of different straw-returning amounts, straw-returning with the stubble of 1 m height could reduce the soil respiration significantly, being a reasonable straw-returning mode.

[Effects of conservation tillage and weed control on soil water and organic carbon contents in winter wheat field].

Taking a long-term (since 2004) straw-returning winter wheat field as the object, an investigation was made in the wheat growth seasons of 2008-2009 and 2009-2010 to study the effects of different tillage methods (rotary tillage, harrow tillage, no-tillage, subsoil tillage, and conventional tillage) and weed management on the soil water and organic carbon contents. No matter retaining or removing weeds, the weed density under subsoil tillage and no-tillage was much higher than that under rotary tillage, harrow tillage, and conventional tillage. From the jointing to the milking stage of winter wheat, retaining definite amounts of weeds, no matter which tillage method was adopted, could significantly increase the 0-20 cm soil water content, suggesting the soil water conservation effect of retaining weeds. Retaining weeds only increased the soil organic carbon content in 0-20 cm layer at jointing stage. At heading and milking stages, the soil organic carbon contents in 0-20, 20-40, and 40-60 cm layers were lower under weed retaining than under weed removal. Under the conditions of weed removal, the grain yield under subsoil tillage increased significantly, compared with that under the other four tillage methods. Under the conditions of weed retaining, the grain yield was the highest under rotary tillage, and the lowest under conventional tillage.

[Effects of different tillage methods and straw-returning on soil organic carbon content in a winter wheat field].

A two growth seasons experiment was conducted to study the effects of different tillage methods, straw-returning, and their interaction on the dynamic change of organic carbon content in 0-20 cm soil layer during the whole growth period of winter wheat. An obvious change was observed in the soil organic carbon content. Treatments with straw-returning had higher soil organic carbon content than treatments with no straw-returning, and conservation tillage induced higher soil organic carbon content than conventional tillage. In all treatments except conventional tillage, the organic carbon content in 0-10 cm soil layer was higher than that in 10-20 cm soil layer. In treatments with straw-returning, the organic carbon content in 0-10 cm soil layer decreased in order of deep soiling (PS) > rotary tillage (PR) > no tillage (PZ) > normal ploughing (PH) > conventional tillage (PC), while that in 10-20 cm soil layer was PC > PS > PR > PH > PZ, suggesting that conservation tillage could improve the organic carbon content in 0-10 cm soil layer. Multi factor variance analysis showed that tillage method, straw-returning, and their interaction had significant effects on the organic carbon content in 0-20 cm soil layer at various growth stages of winter wheat.

[CH4 absorption and its affecting factors in a wheat field with conservation tillage].

In order to understand the relationships between CH4 fluxes and its affecting factors in a wheat field with conservation tillage, the CH4 fluxes in two wheat fields, one with conservation tillage and the another with conventional tillage, were measured in situ by static chamber-GC method, with soil temperature and soil moisture and inorganic nitrogen contents determined at the same time. The results showed that these two fields had an obvious and similar seasonal variation pattern of CH4 fluxes, but the average and seasonal CH4 absorption fluxes differed significantly. In the growth period of wheat, the fields were the sink of CH4, and the CH4 absorption fluxes was in the order of conventional tillage with no straw returning (CN) > conventional tillage with straw returning (CS) > subsoiling with straw returning (PS) > harrowing with straw returning (HS) > rotary tillage with straw returning (RS) > no tillage with straw covered (NS). Comparing with conventional tillage, conservation tillage reduced the CH4 absorption fluxes. In conservation tillage, the CH4 absorption fluxes was positively correlated with soil temperature but negatively correlated with soil moisture content; while in conventional tillage, the CH4 absorption fluxes had no significant correlations with the two factors. In all treatments, there was a significant negative correlation between CH4 absorption fluxes and soil NH4+ -N content.

[Effects of maize-peanut intercropping on economic yield and light response of photosynthesis].

A field experiment was conducted to study the effects of maize-peanut intercropping on the economic yield of the two crops and the light response of their functional leaves' photosynthesis. The results showed that maize-peanut intercropping had an obvious yield advantage, with the total economic yield being 2,896 kg hm(-2) in 2004 and 2,894 kg hm(-2) in 2005, and enhanced the land utilization rate by 14%-17%. For maize's functional leaves, the intercropping enhanced their light saturation point, compensation point, and photosynthetic rate under strong light; while for peanut's functional leaves, it reduced their light saturation point and compensation point but enhanced the apparent quantum yield of photosynthesis and photosynthetic rate under weak light, indicating that maize-peanut intercropping enhanced the utilization efficiency of strong light by maize and that of weak light by peanut, making this intercropping system present an obvious yield advantage.